% 19.用ezsurf绘制曲面
%       x=e^(-s)*cost
%       y=e^(-s)*sint      (0<=s<=8,0<=t<=5pi)
%       z=t
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear
clc
syms s t
assume(s >= 0 & s <= 8);
assume(t >= 0 & t <= 5*pi);
x=exp(-s).*cos(t);
y=exp(-s).*sin(t);
z=t;
ezsurf(x,y,z);